460 THE GENUS ISOETES IN NORTH AMERICA. 
The longest leaves (15 to 25 inches long) we meet with in L. Hngelmanni, I. flaccida, and J, 
Cubana; the shortest (} to 3 inches long) in LZ. pygmea, I. melanospora, and I. saccharata. 
The following classification of our species is proposed as the best I can find, though by no 
means a faultless one :— 
I, Trunk Bitopep. — A. Submerged species with canst’ sre mira or in 4 and 5 with few or many, 
stomata and without peripheral bast-bundles; velum incomplete. 1. J. lacustris. 2. I. pygmea, 3, I. Tuckermani. i, 
echinospora. 5. I. Bolanderi. — B. Amphibious — with abundant packets in the quadrangular leaves. * Without 
peripheral bast-bundles (these are intermediate between the submerged and the truly amphibious species.) + Velum partial. 
I. saccharata. 7. I. riparia. + t Velum ead SZ oagoer gash * * With Siena bast-bundles. { Velum 
i 9. I. Engelmanni, 10. I. Howellii. t+ t Velum complete. I. flaccida. — C. Terrestrial species, maturing when 
entirely out of water, with abundant stomata and peripheral bast- one in the nearly siesta ‘Gi * Velu 
partial or almost wanting. 12. I. melanopoda. 13. I. Butlerit. * * Velum complete. 14. I. Nuttallit. [375 (18)] 
II. TRUNK TRILOBED, numerous stomata and bast-bundles in the quadrangular leaves; velum partial. 15. I. Cubana. 
§5. GEOGRAPHICAL DISTRIBUTION. 
Only a small part of the North American continent has been well explored for Isoétes, and 
there, from Massachusetts to the Chesapeake Bay, they appear abundant enough; farther south, and 
in the whole interior and western part of the continent, they have thus far been found only in a few 
localities. Some species are quite local, as is the case also with many species of the old world, 
while others are widely distributed. Our two northern species are identical with, or closely allied 
to, European forms; all the others are quite distinct from such, so that there is scarcely more than 
a generic analogy between the species of our middle and southern regions with the Mediterranean 
ones or those of other regions of the globe. 
The old Linnean Jsoétes lacustris is the only species atedle has been found to extend from the 
Atlantic to the Pacific States, and it probably occupies a northern belt of the northern hemisphere, 
though it seems not to have been discovered as yet in Asia. The American forms allied to J. echino- 
spora, the other North European species, are the most.common in the belt of northern States as far 
west as Michigan, and have been detected also on the western slope of the Rocky Mountains. Of 
the others, 7. Hngelmanni extends from Massachusetts to Georgia, and westward to Missouri, though 
thus far not found anywhere else west of the Alleghany Mountains. I. flaccida is peculiar to 
Florida, and J. Bolanderi to the lakes of the western mountain chains, the Rocky Mountains as well 
as the Sierra Nevada. J. melanopoda occupies parts of the Mississippi Valley from Central Ilinois 
to Northeastern Texas, while 7. Nuttallii is the only species found in the valley of the Columbia 
River. All the other species seem to be nearly or quite local ;— 7. pygmea, in the Californian Sierra, 
but most of them on the Atlantic border. Thus I. Tuckermani occurs only near Boston, J. saccharata 
on streams emptying into the Chesapeake Bay, and I. melanospora only on that peculiar and botani- 
cally so interesting rock, the Stone Mountain of Georgia. Some species which seemed local have 
lately assumed a little wider range, though yet quite restricted. Among these I mention I. riparia 
of the banks of the lower Delaware River, which occurs also farther north, and /. Butleri, first 
known only from the Indian Territory, now also found in Tennessee. There can be no doubt but 
that some of the apparently local species will yet be found in a more extended area, when botanists 
will include in their researches these obscure and inconspicuous plants. 
From the warmer parts of North America we know only J. Cubana, from Cuba; none have yet 
turned up from Mexico. 3 
The following table will explain itself : — 
